SAN2020

Recently we demonstrated that retrosplenial cortex (RSC) is required for object recognition (OR) memory consolidation. Here, we aimed to study which brain structures interact with the RSC to process OR memory in rats. We selected six brain structures that are connected to the RSC to study their interaction in OR memory formation: perirhinal cortex (PRH), medial prefrontal cortex (mPFC), anteromedial thalamic nuclei (AM), medial entorhinal cortex (MEC), hippocampus (HP) and anterior cingulate cortex (ACC). First, we studied the participation of these structures in OR memory by bilateral infusions of the GABA receptor agonist muscimol. We observed an amnesic effect when inactivating the PRH, mPFC, AM and MEC, but not after HP or ACC inactivation. Then, we studied the functional connections by unilateral inactivation of RSC and each of the six structures in the same (ipsilateral) or the opposite (contralateral) hemisphere. Our results showed an amnesic effect of ipsilateral inactivations of RSC-PRH, RSC-mPFC, RSC-AM, or RSC-MEC. Conversely, contralateral inactivation of RSC-ACC produced memory impairment, while RSC-HP inactivation had no effect on memory. Thus, our ipsilateral inactivation findings reveal that RSC and at least another region involved in OR memory processing are required to form OR memory. In conclusion, our results show that several cortico-cortical and cortico-thalamic pathways appear to be important for OR memory consolidation.